This invention relates to an automotive seat head restraint adjustment mechanism and particularly to a locking mechanism for the head restraint assembly. It provides detents for various extended positions of the head restraint and a bushing with an upper flange containing a wire spring to supply a resistive force for securing the head restraint pad in place.
Motor vehicle manufacturers provide head restraints for occupant seats as a comfort and safety feature. Head restraints provide a surface which the seat occupants can rest their heads against and also provide occupant protection by controlling rearward excursion of the occupant's head in rear impact situations and secondary excursion of the occupant's head in frontal compact situations.
Head restraints can be categorized in several different general types. The so-called integral head restraint or "high back" seat has a seat back with a vertical extension forming a head restraint. Another type of seat has a separate head restraint pad extending upwardly above the seat back and frequently has a mechanism for allowing the vertical position of the pad to be adjusted and positioned for a particular seat occupant. Vertical adjustment of these types of head restraints is typically accomplished by providing one or more posts extending from the head restraint pad into the seat back, with the mechanism mounted within the seat back for allowing the position of the head restraint pad to be adjusted and set at a desired position. As a means of preventing inadvertent removal of the head restraint from the seat back, which could occur during adjustment, a latch or stop may be provided which limits the upward extent of adjustment of the head restraint pad. Further means are often provided for unlatching the stop which enable the head restraint pad to be removed from the seat back for vehicle repair, servicing or retrimming.
While numerous designs for head restraint assemblies of the above type are known, manufacturers of motor vehicle components are constantly striving to increase productivity by simplifying seat assembly. One method of locking the head restraint in different vertical positions uses tubular plastic guides containing the headrest post, which contains V-shaped notches equally spaced along the length of the post. A wire spring connected to the guides engages the notches and provides a resistive force to prevent inadvertent movement of the head restraint pad. One such prior art device, disclosed in U.S. Pat. No. 4,976,493, relies on a D-shaped wire spring to provide the resistive force. While this spring geometry provides an adequate vertical resistive force, the spring only deflects at one place during vertical adjustment of the head restraint, and is therefore subject to early fatigue failure.
Accordingly, it is an object of the present invention to provide a head restraint adjustment mechanism with a new spring geometry which distributes the resistive force applied by the spring during adjustment of the head restraint as evenly as possible. To achieve this object, the top flange of the plastic mounting guides and the spring of the present invention are constructed having a geometry which allows head restraint adjustment forces to be distributed over both ends of the spring rather than be concentrated at a single point. The resulting force distribution is therefore more even than that associated with prior art devices, and the spring design of the present invention therefore has a longer fatigue life as well.